WiredTiger doesn't yet have support for generating deltas when reconciling large pages.

There are some reasonable solutions here:
1. Reduce the maximum size a page grows to. This is the quickest change, but high throughput workloads will suffer – they benefit from large memory pages.
2. Add heuristics to cache management so that pages that are stuck in this repeated, inefficient reconciliation cycle are evicted. This will remove the large pages from cache and alleviate the problem without also harming high-throughput workloads. This change won't require input from the server, except to reset the default memory_page_max.
3. Being able to generate deltas effectively when reconciling such large pages.

See ticket comments for references and further info.